It's all about imaginary brick wall bandpass filters.

On 2020-04-17 11:37, Scott McGrath wrote:

--
Dr. Don Latham  AJ7LL
PO Box 404, Frenchtown, MT, 59834
VOX: 406-626-4304

Hi

Was that +9.8 or -98 dbm ? :)

At -98 they probably could coexist with GPS. Not real clear how well there
system would work at that level though.

Bob

That was +9.8 on the terrrestrial microcell transmitters,

Yes this seems to have been sold with the assurance that the magic brickwall filters with 100db/octave slope will be included in every one.

But the asian manufacturer of said devices will neglect to include them.... and juice the power a wee bit to say +23...

Of course this will hose every GPS system for miles around and for those of us who fly our multi thousand investment in ADS-B will be rendered useless as the ADS-B still uses L1.    In our club’s Cessna 172 the new ADS-B in/out compliant radio stack was 20,000 as we are close to a lot of controlled airspace.

I dropped a note to AOPA on this.  Because remember the entire airway system is now supposed to be managed by aircraft exchanging position, bearing altitude and rate of climb dynamically to each other and ground stations instead of todays radar based system.

And say goodbye to our GPSDO’s

On Apr 17, 2020, at 2:59 PM, Bob kb8tq kb8tq@n1k.org wrote:

Hi

Was that +9.8 or -98 dbm ? :)

At -98 they probably could coexist with GPS. Not real clear how well there
system would work at that level though.

Bob

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The original article said 9.8dBW.  I guess 10 WATTS?  Kind of unusual unit expression....

(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG

On Friday, April 17, 2020, 4:38:36 PM EDT, Scott McGrath <scmcgrath@gmail.com> wrote:  

That was +9.8 on the terrrestrial microcell transmitters,

Yes this seems to have been sold with the assurance that the magic brickwall filters with 100db/octave slope will be included in every one.

But the asian manufacturer of said devices will neglect to include them.... and juice the power a wee bit to say +23...   

Of course this will hose every GPS system for miles around and for those of us who fly our multi thousand investment in ADS-B will be rendered useless as the ADS-B still uses L1.    In our club’s Cessna 172 the new ADS-B in/out compliant radio stack was 20,000 as we are close to a lot of controlled airspace.

  I dropped a note to AOPA on this.  Because remember the entire airway system is now supposed to be managed by aircraft exchanging position, bearing altitude and rate of climb dynamically to each other and ground stations instead of todays radar based system.

And say goodbye to our GPSDO’s

On Apr 17, 2020, at 2:59 PM, Bob kb8tq kb8tq@n1k.org wrote:

Hi

Was that +9.8 or -98 dbm ? :)

At -98 they probably could coexist with GPS. Not real clear how well there
system would work at that level though.

Bob

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and follow the instructions there.

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And the competition has/is putting up a gazillion cubesats to screw up
another of my little pleasures, astronomy. Bah. It's enough to make you
want to go out and stand right next to somebody.
Don

On 2020-04-17 14:37, Scott McGrath wrote:

--
Dr. Don Latham  AJ7LL
PO Box 404, Frenchtown, MT, 59834
VOX: 406-626-4304

On 4/17/20 2:04 PM, Taka Kamiya via time-nuts wrote:

dBW it is. It's what's used in transmitter license filings, since most
transmitters are Watts, kilowatts, or megawatts. Very few licenses
issued for <1 Watt.

One also needs to know the EIRP. 10 dBW into a 20dBi sector antenna with
a downtilted horizontal beam that's 100 degrees wide means that from an
interference standpoint, it's like the transmitter is a kilowatt from an
isotrope.

Seems to me that both GPS receivers and Ligado's transmitters are going to
need the
"brick-wall" filters.  I wonder how lossy such filters will be when sized
to fit in handheld
GPS receivers, smart phones, and (especially) GPS watches.

On the other hand, it may be that many time-nuts will not live close enough
to any of
Ligado's terrestrial sites to be appreciably bothered.

It's a difficult situation- we won't know how big the problem is until
Ligado goes on the air,
yet the time to complain is now, before any rulemaking occurs or
construction permits are
granted.

Test results on a wide variety of commonly-used GPS receivers would sure be
nice.

Dana

On Fri, Apr 17, 2020 at 6:14 PM djl djl@montana.com wrote: